Well the there is only a difference if you are postulating that the source of inertial mass on Earth is different to that on other planets. I assume that you are saying that the Earth only looks to have a gravitational field because it is accelerating upwards at 9.81m/s. But the equivalence principle is telling us something very fundamental about the nature of the gravitational coupling and a bodies resistance to acceleration, we don't know what yet. I'm not arguing that naively one could think the Earth is an upward accelerating flat shape, though the rate of the acceleration is bizzrely dependent on where in the world you are, if you assume its flat. If you assume its spherical then a pattern emerges. But let me give it a go anyway in a minute. The Earth must have a gravitational interaction from its mass as well. The equivalence principle is a two way thing.
Lets assume the world is a disc ending at the Antarctic as I've not heard of anyone falling off (maybe that why Oates' walk took so long). I assume that using the Antarctic as the discontinuity involves calling the fewest people liars. Ok to give the Earth a diameter ill generally use the distance we have today, most of the world has been driven Canada-Chilie, France-Korea the length of Africa. So Ill assume that the radius of a disc Earth is of order 12'000km (the length of the Americas plus a bit for good luck). The depth of the Earth becomes a bit of a challenge I suppose. We can estimate the mass of the Iron needed to make our field. Or look at seismic data, well I'll plump for a middle of the road, conservative 3'000km to minimise the number of scientists that need to be in on the conspiracy. That gives the Earth a volume of 36'000'000'000'000 cubic metres. If we assume its made of water (absurdly conservative but i don't care) which ways 1 tonne per cubic meter that gives us a grand total of 36'000'000'000'000Kg. So the Earth is not light with the exception of the radius every one of those calculations was absurdly conservative so the gravitational mass of the Earth is relevant. So the discussion as to the nature of gravity is as important on Earth as it is everywhere else. If the Earth weighed a tonne then I'd probably agree with you.
Part two might be on the action of the universe if the whole universe is accelerating at 9.81 m/s in the same direction. Though I can't really be bothered because if you have decided the world is flat, lets be honest a reasoned argument is unlikely to change your mind. Because every thread comes back to a conspiracy theory so really science has nothing to do with it, other than showing off that you've found the wiki page for teh equivalence principle or a dusty high school physics text book.